1. Field of the Invention
The present invention relates to an information-recording medium that uses light to recording information and to play back or erase recorded information, to a method for manufacturing such an information recording medium, to a method for recording and playing back information and to a method for erasing information, and more specifically it relates to an information-recording medium that is capable of recording high-density information and a method for manufacturing such an information-recording medium.
2. Description of the Related Art
Magneto-optical discs and DVD-RAMs are known as information-recording media which use light to recording information and to play back or erase recorded information. In information-recording media of the past, the medium was formed by recording regions (land parts) that record information and separating region (groove parts) that separate adjacently arranged recording regions from each other, and a protective film, a recording film, a protective film and a reflective film being laminated in that order along the pattern of a convex-concave configuration reflecting the land parts and the groove parts which are formed on a surface of a transparent substrate.
A laser beam is used for the recording, playback, and erasing of information, recording marks being applied to a part of the recording film corresponding to the recording region. By reducing the spacing between the land and groove parts for the purpose of recording more information, the density of the information recording is increased.
In an information-recording medium of the past, however, if the spacing between the land and groove parts is reduced in an attempt to record more information, the recording marks of recorded information spill over from the land parts to the groove parts.
When the recording marks spill over from the land parts to the groove parts, in an information erasing operation, incomplete erasure can occur, the result being that information from neighboring land parts are read simultaneously in the next play backing operation, this phenomenon being generally call crosstalk.
The information-recording medium that is disclosed in the Japanese Unexamined Patent Publication (KOKAI) No. 9-190649 reduces the crosstalk from the header region by displacing the pre-pit portion that is formed in a region placed in front of the recording region (the header region) in towards the direction of the inner circumference with respect to a center portion of the land part.
The occurrence of crosstalk in an information-recording medium of the past was an unavoidable problem when recording information at a high density.
With the information-recording medium that is disclosed in the Japanese Unexamined Patent Application publication H9-190649, although the crosstalk from the header region is reduced, crosstalk from the recording region was not reduced.
Accordingly, it is an object of the present invention to improve over the drawbacks as noted above in the prior art, by providing an information-recording medium, a method for manufacturing such an information-recording medium, a method for recording and playbacking information and a method for erasing information, so that the crosstalk generated when the play backing operation can be reduced and the recording information with high-density can be realized.